“Our findings show that children, particularly those under the age of 10, experience a protective effect against IBD if they live in a rural household,” Dr. Eric Benchimol, the study’s lead author, said in a press release.

“This effect is particularly strong in children who are raised in a rural household in the first five years of life. These are important findings, since our previous work shows that the number of very young children being diagnosed with IBD has jumped in the past 20 years,” he said. “The findings also strengthen our understanding that environmental risk factors that predispose people to IBD may have a stronger effect in children than adults.”

The study focused on the provinces of Alberta, Manitoba, Nova Scotia and Ontario. Researchers found 45,567 patients diagnosed with IBD in the four provinces between 1999 and 2010.

Most — 38,905 — lived in cities. But 6,662 were from rural areas.

The team calculated the incidence of IBD in rural areas at 30.72 per 100,000 person-years, versus 33.16 per 100,000 in urban areas.

“We’ve known that in addition to genetic risk factors, environmental factors have been associated with the risk of developing IBD,” Benchimol said. “But this new study demonstrates the importance of early life exposure in altering the risk of IBD, and that needs further study.”

“Canada has one of the highest rates of IBD in the world, with most cases diagnosed in individuals between the ages of 15 and 30, and an increasing incidence seen in children under the age of 10,” said Mina Mawani, president and chief executive officer of Crohn’s and Colitis Canada. “We are happy to partner and collaborate with CanGIEC [the Canadian Gastro-Intestinal Epidemiology Consortium] in the effort to better understand these diseases. The results of this study provide additional knowledge of the risk factors associated with a diagnosis of Crohn’s disease or ulcerative colitis.”

Although scientists are unsure why IBD is increasing, urbanization could be playing a role. The reason is that the mix of bacteria in our gut can differ from environment to environment, particularly early in life. So we can be at higher or lower risk of developing bowel disease, depending on whether we live in a rural or urban environment.